1. Field of the Invention
Present invention relates to a C polymer composition containing a nanostructured hollow-carbon material and a liquid-crystalline polymer, and to a molded article thereof.
2. Description of Related Art
It has been known that a liquid-crystalline polymer has excellent heat-resistant property, mechanical strength, and electrical property (e.g. dielectric property). In recent years, by taking advantage of such properties, he liquid-crystalline polymer has been used as a highly functional polymer material (engineering material) which can replace metals and ceramics in various fields such as electrics, electronics, machinery, automobile, aircraft, and medical services, and particularly, has been known as a material suitable electrical and electronic parts having for thin portions or complicated shapes.
However, in the case of melt-molding the liquid-crystalline polymer to obtain a molded article (useful for a part) which is a long object, warping sometimes occurs along a longitudinal direction of the molded article. Also, in the case where the molded article has a flat shape, there is the tendency that the warping easily occurs. Since there is increasing demands for much more reductions in thickness and size as well as more complicated shape due to the trend in recent electrical and electronic parts toward reductions in weight, thickness, and size, the warping is more easily generated in the molded articles having such shapes, and the generated warping tends to cause adverse effects on properties of the parts. Therefore, in producing electric and electronic parts by using the liquid-crystalline polymer, achievement of low warping of a molded article to be obtained is an important issue.
Various factors have been suggested as the cause for the generation of the warping in molded articles. One of them is a polydomain (liquid-crystalline phase) having a liquid-crystalline state without entanglement even in a molten state, which is easily formed due to rigid molecules of the liquid-crystalline polymer. The polydomain has a behavior that molecular chains are prominently oriented toward a direction of a flow due to shearing in molding, which may result in generating the warping. Namely, in the case of melt-molding (e.g. injection molding) the liquid-crystalline polymer or the composition containing liquid-crystalline polymer, it is assumed that the warping is easily generated since the prominent orientation of the liquid-crystalline polymer in the flow direction of the molten product (hereinafter sometimes referred to as “MD”) causes a considerable large difference in shrinkage between MD and a direction perpendicular to MD (hereinafter sometimes referred to s “TD”), i.e. large anisotropy of mold shrinkage rate (see, JP-A-2000-53849). JP-A-2000-53849 discloses that it is possible to obtain a molded article that is improved in warping by reducing the anisotropy by mixing a polyester-based thermoplastic elastomer with a thermotropic liquid-crystalline polymer. Also, JP-A-2006-186122 discloses that the anisotropy of mold shrinkage rate in a case for accommodating solid-state imaging device if the case is made from a liquid-crystalline polymer composition comprising a liquid-crystalline polymer and a filler (filler made from inorganic material) such as an inorganic plate-like filler or an inorganic needle-like filler; and discloses that the case is sufficiently suppressed in warping and is excellent in heat conductivity.